I get a buzzing noise whenever the sub is powered on and connected to the preamp. Tried it on several amps; same result.

I would check the caps on the power supply. They are rather large electrolytic capacitors that will look like they burst and/or leaking. When these die, the caps ground and the sub will make a loud buzzing sound. If you are handy with a soldering iron you can replace them yourself. Replace them with the same voltage or a little bigger and same with the size.

If the cap. says 16v 4700pF on it, for example, a 20v 5300pF or a 16v 6200mF cap. will work for this application.

Things to check:
1. With your multi meter, measure from left ground to right ground. What do you get? Measure from each input ground to chassis. What do you get there.

2. Get or make a pair of shorting plugs. Plug those into the inputs. Power on. Hum there or gone?

3. Turn the pre-amp on. Connect. Level of hum change with preamp on?

4 additional information. How efficient are your speakers? This is a big amp, high-efficiency speakers may show some noise, while low-efficiency speakers won't.

A trip back to the shop may be indicated, too.

If your tv uses rca a jacks to connect it up to the reciever, You coul try what is called a ground loop iceilator, It hooks up to the patch cord,If they are still availible.They were use on car Stereo,s when you have a amp hook up to it,In some vehicles you would get a ground loop hum. Radio Shack might still sell them. You could try one.It work for me with a (Carver) Power amp that i use to own.

You DO realize the preamp is duplicating stuff in the Nad C372, right? This Preamps adds nothing but PHONO connectivity and control. That's why they're called "preamps".

Register and download the manual for free at retrevo.com

http://www.retrevo.com/support/NAD-C372-Amps-manual/id/8043dj592/t/2/

http://www.retrevo.com/support/Mirage-OMNI-S10-Subwoofers-manual/id/14438ag918/t/2/


Model 2100 Picture and article:

Use the Sub Out pair on the Preamp (joined by an RCA Y-cable) for the Sub Input on the sub (duh):

http://www.hometheaterhifi.com/preamplifiers/362-a-secrets-preamplifier-and-power-amplifier-review.html?showall=1

Run RCA from the Preamp Main Out to the C372 Aux In to hear any sources attached to the preamp.

Or, if you don't NEED the preamp because you don't have a turntable,ditch the preamp and connect the sub using the speaker outputs on the NADS, according to the manual.

Try moving your guitar around and oriented differently as it MAY be picking up magnetic fields from equipment in the area. Some pickups really are sentive to interference.

The effects for modeling MAY have a noise gate that requires a certain signal level before unmuting which would explain why you have to be playing to open the gate and hear noise that is really there all teh time but muted.

It looks as though you have ripple noise that amplifies into the output. First of all check if the mains voltage is going down to produce the low voltage hum. If not you will have to check the DC filter capacitors , couple in parallel to confirm the capacitor. IF the buzz is still coming through then you will have to isolate the preamp and wait it the fault is coming in. If not connect the preamp output to another amp to hear the same buzz to confirm the preamp to be faulty. If so you will have to trace by a voltage check when the buzz occurs to confirm if the preamp IC or the selector Ic is faulty. Some logic IC's can also produce this noise on static switching. If teh noise is appearing on both the channels, then I would still bet on the power section. So check once again on the rectifier/ regulators and capacitors. Hope this advice helps. Good day

ur sub wont buzz due to bad speaker. either u have a faulty preamp or power amp. yes it can be repaired and will not cost much. if it is loud and annoying, get it repaired. sometimes subs emit low hum when powered up. this is the way the are desinged.

Hello anne845,

It sounds like the installer wired the amp remote turn-on terminal to an "accessory" lead in your vehicle. Many stock radios do not have a dedicated amp turn-or lead and the alternative is to connect the amp to a switched power source (ignition or accessory). This means the amp turns on whenever you turn on the vehicle ignition, often resulting in a thumping from the subs. It is a perfectly satisfactory alternative, and will not damage either the amp or the sub. But it's irritating.

If the thumping is objectionable, have your installer wire a SPST (Single Pole, Single Throw) toggle switch inline with the turn-on wire. The switch should be mounted so it is accessible by the driver, and whenever you turn on the radio, turn on the toggle switch.

Hope this helps.

Hi chupetin2

If the problem is present with ONLY the speakers connected, that is no other powered devices like subs, or input/output cables, it will be a power supply problem inside the amp. If you have electronic fault finding skills, there will probably be a capacitor in a regulated rail that has failed.
If you do have a sub connected, be sure it is powered from the same mains source as the amp, or at least a GPO that is on the same phase. Different phases will induce mains hum, as will multiple earths. Try also temporarily moving the amp(whilst monitoring the hum) from where it is sitting and see if the hum is being induced into the amp by any other devices

Happy to talk to you more about this. Just ask:)

regards
robotek

You didn't say is your sub active or passive.If its active first check signal cables from theater system,power line of the sub, it has to be the same phase as the system.If its passive take a voltmeter disconnect the sub from the system and measure for DC voltage on the SUB output on the system when its OFF.If DC voltage is present your amp is damaged.It can also be that the preamp circuit for the sub doesn't mute the input when unit is on stand by and you hear frequency of your power supply (50-60Hz) on the sub